Hi Adam,
On 12/07/2011 11:34 AM, Laurent Pinchart wrote:
Hi Adam,
On Wednesday 07 December 2011 09:02:42 Adam Pledger wrote:
Hi Laurent,
Firstly, please accept my apologies, for what is very probably a naive
question. I'm new to V4L2 and am just getting to grips with how things
work.
No worries.
I'm using a tvp5151 in bt656 mode with the Omap3 ISP,
Please note that BT.656 support is still experimental, so issues are not
unexpected.
as described in this thread (Your YUV support tree + some patches for bt656,
based on 2.6.39):
http://comments.gmane.org/gmane.linux.drivers.video-input-
infrastructure/39539
I am able to capture some frames using yavta, using the media-ctl
configuration as follows:
media-ctl -v -r -l '"tvp5150 3-005d":0->"OMAP3 ISP CCDC":0[1], "OMAP3
ISP CCDC":1->"OMAP3 ISP CCDC output":0[1]'
media-ctl -v --set-format '"tvp5150 3-005d":0 [UYVY2X8 720x625]'
media-ctl -v --set-format '"OMAP3 ISP CCDC":0 [UYVY2X8 720x625]'
media-ctl -v --set-format '"OMAP3 ISP CCDC":1 [UYVY2X8 720x625]'
This yields this:
[snip]
Looks good.
The following works nicely:
yavta -f UYVY -s 720x625 -n 4 --capture=4 -F /dev/video2
The problem comes when I try to use gstreamer to capture from
/dev/video2, using the following:
gst-launch v4l2src device="/dev/video2" !
'video/x-raw-yuv,width=720,height=625' ! filesink location=sample.yuv
This fails with:
ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Failed
getting controls attributes on device '/dev/video2'.
Additional debug info:
v4l2_calls.c(267): gst_v4l2_fill_lists ():
/GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
Failed querying control 9963776 on device '/dev/video2'. (25 -
Inappropriate ioctl for device)
My question is, should this "just work"? It was my understanding that
once the pipeline was configured with media-ctl then the CCDC output pad
should behave like a standard V4L2 device node.
That's more or less correct. There have been a passionate debate regarding
what a "standard V4L2 device node" is. Not all V4L2 ioctls are mandatory, and
no driver implements them all. The OMAP3 ISP driver implements a very small
subset of the V4L2 API, and it wasn't clear whether that still qualified as
V4L2. After discussions we decided that the V4L2 specification will document
profiles, with a set of required ioctls for each of them. The OMAP3 ISP
implements the future video streaming profile.
I'm not sure what ioctls v4l2src consider as mandatory. The above error
related to a CTRL ioctl (possibly VIDIOC_QUERYCTRL), which isn't implemented
by the OMAP3 ISP driver and will likely never be. I don't think that should be
considered as mandatory.
I think that v4l2src requires the VIDIOC_ENUMFMT ioctl, which isn't
implemented in the OMAP3 ISP driver. That might change in the future, but I'm
not sure yet whether it will. In any case, you might have to modify v4l2src
and/or the OMAP3 ISP driver for now. Some patches have been posted a while ago
to this mailing list.
Here was my submission for ENUM_FMT support:
http://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg29640.html
I submitted this in order to be able to use the omap3-isp with
GStreamer. I missed the discussion about V4L2 "profiles", but when I
submitted that patch we discussed whether ENUM_FMT was mandatory. After
I pointed out that the V4L2 spec states plainly that it _is_ mandatory,
I thought Laurent basically agreed that it was reasonable.
Laurent, what do you think about adding ENUM_FMT support now?
I realise that this might be something borked with my build dependencies
(although I'm pretty certain that v4l2src is being built against the
latest libv42) or gstreamer. Before I start digging through the code to
work out what is going on with the ioctl handling, I thought I would
check to see whether this should work, or whether I am doing something
fundamentally silly.
-Michael
MATRIX VISION GmbH, Talstrasse 16, DE-71570 Oppenweiler
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